1. Field of the Invention
The present invention relates to a method and apparatus for testing the clamp strength of an electrical connection, and in particular to a method and apparatus for achieving such testing which simulates worst case configurations for a wire bundle.
2. Description of the Prior Art
Solderless electric clamp connections of the type described in Siemens brochure SFR F12-F1545 November, 1976, "Clamp Connection" are known in the art. Such connectors have a deformable metallic clamp comprised of opposed legs which are initially spaced apart to receive a bundle of wires and are subsequently forced together to retain the wires against a pin. As described in the above brochure, assembly of such a clamp is generally undertaken by the use of a pistol which is "loaded" with a clamp and an insulated wire end is inserted into the clamp and pressed therein by actuating the trigger of the pistol. The tip of the pistol containing the clamp and wire assembly is positioned over a pin to which the clamp is to be attached and pressure applied to force the legs of the clamp around the pin fixing the clamp assembly thereto. A high strength electrical connection is thus achieved without the use of solder.
According to prescribed testing procedures, the strength of such a connection is measured by testing the gripping strength of the clamp to the pin, with little or no attention given to the mechanical strength of the wire-clamp attachment. Such testing generally proceeds by applying a so called removal tester to the pin which has an element which is pushed against the clamp on the pin and the applied force is measured by a calibrated spring contained in the grip of the removal force tester. In order to pass the test, the clamp cannot be displaced when forces less than a specified maximum are applied.
Such a testing procedure is insufficient because it does not test the clamping strength of the clamp surrounding the bundle of wires. Even though such an attachment may be tight and exhibit sufficient strength when first assembled, a loosening of this attachment can occur when the wires within the insulation move relative to the clamp pin. In the processing of multiple wire conductors, the individual wires may during assembly initially arrange themselves in bundles which due to later movement of the conductor can shift. For example, a bundle of wires may initially be arranged generally in circular cross section but may subsequently realign themselves in a flattened pattern or straight line consisting of adjacent wires. When this occurs, even though the clamp may have initially been applied to the bundle of wires with sufficient clamping strength, the movement of the wires beneath the closed clamp may result in a loosening of the wire because the individual clamp legs do not have sufficient spring tension to automatically compensate for a change in wire bundle cross section.
It is thus a problem in the art to provide a method and apparatus for testing the mechanical strength of a solderless electrical connection of the type described above which can account for the extreme cases wherein the wires are initially arranged in a circular pattern and later re-distribute themselves into an essentially straight configuration.